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S Reichlin

Publications and source records attributed to S Reichlin.

At least 19 recordsLinked to original sources
PubMed1992

Interaction of an alpha-melanocyte-stimulating hormone-diphtheria toxin fusion protein with melanotropin receptors in human melanoma metastases.

A hybrid toxin targeted to melanotropin receptors and selectively cytotoxic to melanoma cell lines in vitro has recently been developed. The toxin, a recombinant fusion protein (designated DAB389-MSH), contains the peptide sequences of alpha-melanocyte-stimulating hormone (alpha-MSH) and the catalytic (cytotoxic; Fragment A) and lipophilic (part of Fragment B) domains of diphtheria toxin. In the present study, binding of DAB389-MSH to melanotropin receptors in biopsy specimens of human and mouse melanoma metastases was assessed by measuring its ability to inhibit binding of a radiolabeled, superpotent analogue of alpha-MSH (125I-[Nle4,D-Phe7]-alpha-MSH; 125I-NDP-MSH) and comparing its potency in this system with those of the established ligands NDP-MSH and alpha-MSH. Radioligand binding to tissue sections in vitro was localized and quantified by autoradiography and image analysis. DAB389-MSH inhibited binding of 125I-NDP-MSH to experimental murine B16-F1C23 melanoma metastasis tissue and to melanoma metastases of three patients. In both mouse and human melanoma tissues, concentration-response relationships for DAB389-MSH-mediated inhibition of 125I-NDP-MSH binding were parallel, and its maximal effects were comparable in magnitude, to those of NDP-MSH and alpha-MSH. Half-maximal peptide concentrations for inhibition of 125I-NDP-MSH binding to mouse melanoma tissue sections were: NDP-MSH, 0.63 nM; alpha-MSH, 3.14 nM; and DAB389-MSH, 10.1 nM. In human melanoma tissues, the respective half-maximal peptide concentrations for inhibition of 125I-NDP-MSH binding to mouse melanoma tissue sections were: NDP-MSH, 1.80 nM; alpha-MSH, 2.43 nM; and DAB389-MSH, 11.9 nM. Taken together, these results suggest that NDP-MSH, alpha-MSH, and DAB389-MSH bind to a common melanotropin receptor in human metastatic melanoma cells. Since previous work has shown that melanotropin receptors are detectable in melanoma metastases of about 80% of human patients, malignant melanoma cells of many patients may be susceptible to killing by the melanotropin receptor-targeted cytotoxin DAB389-MSH.

Animals↗
PubMed1992

The angiotensin AT2 receptor stimulates protein tyrosine phosphatase activity and mediates inhibition of particulate guanylate cyclase.

The signalling mechanism and cellular targets of the AT2 receptor are still unknown. We report that angiotensin II (Ang II) inhibits basal and atrial natriuretic peptide stimulated particulate guanylate cyclase (pGC) activity through AT2 receptors in rat adrenal glomerulosa and PC12W cells. This inhibition is blocked by the phosphotyrosine phosphatase (PTPase) inhibitor orthovanadate but not by the Ser/Thr phosphatase inhibitor okadaic acid, suggesting the involvement of a PTPase in this process. Moreover, Ang II induces a rapid, transient and orthovanadate sensitive dephosphorylation of phosphotyrosine containing proteins in PC12W cells. Our findings suggest that AT2 receptors signal through stimulation of a PTPase and that this mechanism is implicated in the regulation of pGC activity. This observation is also the first example of hormonal inhibition of basal pGC activity.

Angiotensin II↗
PubMed1992

Somatostatin depleting potency of cysteamine-related thiols and amines in the rat: structure-activity relation.

Cysteamine, a potent duodenal ulcerogen, stimulates gastric acid and gastrin secretion and decreases immunoreactive somatostatin (IRS) from the gut and hypothalamus of the rat. To elucidate the structural requirements for this effect, we tested a series of cysteamine analogs for their IRS decreasing activity in comparison with their nucleophilic and reducing potencies. Adult female rats were sacrificed 4 hr after p.o. administration of the test chemicals given in molar equivalents to 30 mg/100 g of cysteamine-HCl. IRS decreasing activity in gastric mucosa, expressed as percentage of controls is listed in descending order: cystamine (55%), cysteamine (59%), 2-dimethylaminethanethiol (59%), ethylamine (66%), 1,3-propanedithiol (70%), propylamine (75%) and 3-aminothiophenol (79%). The following thiols and amines had no IRS decreasing effect (80% of controls): L-cysteine, ethanethiol, 1-propanethiol, penicillamine, dimercaprol, 1-4-dithiothreitol, ethanolamine, propionitrile, n-butyronitrile, o-, m- or p-aminophenol. The aryl 2-, 3- or 4-aminothiophenols, unlike most of their aminophenol analogs also decreased immunoreactive prolactin in the pituitary by 38 to 78%. IRS decreasing activity was independent of the reducing potency of cysteamine derivatives but was correlated significantly (r = 0.793, P < .01) with electron affinity of -SH, -NH2, -OH and -CN radicals in terminal alkyl chemicals. The structural requirement for decreasing activity is the presence of either -SH and -NH2 on a 2 to 3 carbon alkyl or aryl molecule. Both radicals when present together increase potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMed1992

High-sensitivity serum calcitonin assays applied to screening for thyroid C-cell disease in multiple endocrine neoplasia type 2A.

UNLABELLED: Two serum calcitonin assays with sensitivities < or = 10 pg/mL were compared to our standard radioimmunoassay (sensitivity 100 pg/mL) in multiple endocrine neoplasia type 2A (MEN 2A) screening. Values from the Nichols displacement radioimmunoassay averaged 38% higher than values from the CIS immunoradiometric assay; values from both were highly correlated, r = 0.845. In three individuals, both of the newer assays revealed abnormalities in pentagastrin tests three to four years before abnormalities were detected by the standard assay. Pentagastrin tests after total thyroidectomy were assayed by the newer methods in patients with medullary thyroid carcinoma (MTC) diagnosed at initial testing (group I); in patients with early MTC diagnosed by prospective screening (group II); and in patients with pure C-cell hyperplasia detected by prospective screening (group III). At least 64% of group I, at least 25% of group II, but none of group III had detectable postoperative C-cell function. CONCLUSIONS: 1) The previous estimate of 12 years as median age of onset of C-cell disease in MEN 2A is probably three to four years too old. 2) Patients diagnosed with early MTC by screening had not necessarily skipped a preneoplastic phase of C-cell hyperplasias. At least some early disease was not detected by the standard assay. Higher sensitivity assay should improve screening for C-cell disease by earlier disease detection. 3) Biochemical cure by thyroidectomy after the development of MTC is not as frequent as previously thought, but the apparent cure rate of pure C-cell hyperplasia remains 100%.

Adolescent↗
PubMed1991

Carbamazepine and phenytoin inhibit somatostatin release from dispersed cerebral cells in culture.

To elucidate the mechanism by which carbamazepine lowers somatostatin concentration in cerebrospinal fluid of humans, the effect of carbamazepine on secretion of this peptide was studied in rat cerebral cell cultures. Concentrations of carbamazepine within the therapeutic range (4 x 10(-5) M) inhibited spontaneous release of somatostatin and blocked secretory responses to the epileptogen, picrotoxin, and to the cyclic cAMP stimulator forskolin. One of the proposed mechanisms of carbamazepine action is that it binds to adenosine receptors, but in this study, aminophylline, an adenosine antagonist, in a concentration as high as 2.4 x 10(-4) M, did not reverse carbamazepine effects. Carbamazepine suppression of picrotoxin, however, was overcome by exposure to veratridine, a sodium channel-active compound. This finding supports the hypothesis that carbamazepine acts by binding to sodium channels. Phenytoin, another anticonvulsant with many similar properties, also blocked picrotoxin-induced somatostatin release at a concentration of 10(-4) M, and its effects were also reversed by veratridine at a concentration of 10(-5) M. These findings clarify the mechanism by which carbamazepine and phenytoin act in epilepsy and trigeminal neuralgia.

Animals↗
PubMed1991

Regulation of cholecystokinin octapeptide secretion by rat cerebral cortical cells in primary culture.

The regulation of cholecystokinin octapeptide (CCK-8) secretion was studied using a fetal cerebral cortical cell culture system. After 2-3 weeks in culture, the cells were utilized for short-term release experiments. CCK-8 was measured by RIA and its identity was confirmed by HPLC. Depolarization of the cells with K+ (6 x 10(-2) M) evoked CCK-8 release and this response was blocked by the Ca++ channel blocker verapamil (2 x 10(-5) M) and by Ca++ free medium. The Na+ channel opener veratridine (10(-4) M) stimulated CCK-8 release and was blocked by the Na+ channel blocker tetrodotoxin (10(-6) M) and by Ca++ free medium. The adenylate cyclase activator forskolin (10(-5) M) markedly increased CCK-8 secretion. No changes in CCK-8 release were induced by epinephrine, norepinephrine, dopamine, acetylcholine, or 5-hydroxytryptamine at 10(-5) and 10(-4) M, but gamma-aminobutyric acid (GABA) at 10(-4) M inhibited CCK-8 release. GABA inhibition was reversed by the GABA antagonist picrotoxin (10(-4) M). Both picrotoxin (10(-4) M) and bicuculline (10(-3) M), another GABA receptor antagonist, alone stimulated CCK-8 secretion. These data show that CCK-8 secretion by cerebral cortical cells 1) is stimulated by cell membrane depolarization in a calcium-dependent fashion, 2) is regulated by cAMP, 3) is unaffected by the neurotransmitters characteristic of corticopetal systems, 4) is tonically inhibited by GABA.

Animals↗
PubMed1990

Gomori-positive astrocytes in primary culture: effects of in vitro age and cysteamine exposure.

Gomori-positive astrocytes have been identified in the periventricular brain in situ and in diencephalic explants on the basis of their endogenous peroxidase activity, affinity for chrom alum hematoxylin, and orange-red autofluorescence. To facilitate analyses of their functional properties, we sought to identify these cells in dissociated fetal rat brain cultures. Astrocytes containing cytoplasmic inclusions with the above tinctorial and fluorescent properties represented less than 1% of cultured astrocytes at day 10 in vitro (DIV). There was a marked increase in the fraction of Gomori-positive astrocytes and their granule content between 10 and 46 DIV. As in situ, the peroxidase activity appeared to be non-enzyme-mediated insofar as it catalyzed diaminobenzidine oxidation over a wide range of pH (3-11) and could not be inhibited by tissue preheating or the catalase inhibitor, aminotriazole. Metalloporphyrins probably mediate both the pseudoperoxidase activity and autofluorescence in these cells. Cysteamine and cystamine, but not ethanolamine or L-cysteine, induced a massive accumulation of Gomori-positive astrocytes when administered from DIV 6-18. Alterations of the redox microenvironment or induction of porphyrin/heme biosynthetic enzymes may be the mechanisms responsible for this cyst(e)amine effect. Dissociated rat brain culture enriched for Gomori astroglia should provide ample opportunity to investigate the functional properties of these cells.

Animals↗
PubMed1990

Melanotropin receptors of murine melanoma characterized in cultured cells and demonstrated in experimental tumors in situ.

Cultured melanoma cells are known targets for the pigment-inducing actions of melanotropins such as alpha-melanocyte-stimulating hormone (alpha-MSH). The objectives of the present studies were to determine the binding properties and functional relevance of MSH binding sites in a mouse melanoma cell line and to determine whether MSH receptors are expressed in situ. The binding properties of MSH receptors in intact cells of a highly metastatic, highly MSH-responsive mouse melanoma cell subline (B16-F10C23) were determined using a radiolabeled, biologically active preparation of the superpotent alpha-MSH analogue, [Nle4,D-Phe7]-alpha-MSH (125I-NDP-MSH). A single high-affinity class of binding site was detected (Kd for NDP-MSH, 5.6 x 10(-11) M; Kd for alpha-MSH, 2.6 x 10(-9) M as determined by Scatchard analysis and heterologous inhibition assays, respectively). alpha-MSH showed nearly identical concentration-response relationships in the radioreceptor assay (inhibition of 125I-NDP-MSH binding) and a bioassay (stimulation of intracellular cyclic AMP accumulation). Furthermore, the respective potencies of three melanotropins, NDP-MSH, alpha-MSH, and adrenocorticotropic hormone, in binding and biological assays were highly correlated. These results indicate that the 125I-NDP-MSH binding site represents the functional MSH receptor. Tumors were induced by inoculation of C57BL/6 mice with B16-F10C23 cells, and the presence of 125I-NDP-MSH binding sites was determined by in situ radiolabeling of frozen tissue sections followed by autoradiography. Specific MSH binding sites were distributed throughout the tumor tissue, but not in associated fibrovascular elements or in neighboring nonmelanoma tissues. As in cultured B16-F10C23 cells, melanotropins inhibited 125I-NDP-MSH binding to tissue sections in a concentration-dependent manner. These results support the hypothesis that functional MSH receptors are expressed in melanoma in situ, suggesting that the activities of melanoma cells in vivo may be subject to modulation by endogenous melanotropins. The methods described will be applicable for studies of the expression and regulation of MSH receptors in human melanoma and other target tissues.

Animals↗
PubMed1990

Acetylcholine stimulates the secretion of corticotropin-releasing factor from primary dissociated cell cultures of the rat telencephalon and diencephalon.

Corticotropin-releasing factor (CRF-41) immunoreactive neurones in the CNS are widely distributed; although the major concentration is in the parvocellular division of the paraventricular nucleus, there are also large clusters of CRF-containing neurones in the brainstem, limbic system and cerebral cortex. In this study, we sought to determine whether dispersed rat brain cells cultured in vitro are capable of secreting CRF immunoreactivity. In both telencephalic and diencephalic cultures CRF content of the cells increased from day 7 to 28. This effect was greatest in cells raised in media containing 10% fetal calf serum and 10% heat inactivated horse serum as compared with media containing 10% fetal calf serum and 10% NuSerum. Exposure of the cells to 56 mM K+ or to 10(-9) M acetylcholine caused a release of CRF which was calcium dependent. The effect of acetylcholine was antagonised by atropine (10(-6) M). The CRF immunoreactivity in both types of cell produced two peaks on gel chromatography; one of which eluted with the void volume and the other of which co-eluted with standard CRF-41. However, only the mature peptide was detected in media from cells stimulated with potassium. We conclude that cell cultures of the rat diencephalon and telencephalon produce immunoreactive CRF-41 and that immunoreactive CRF-41 secretion in both diencephalic and telencephalic cells is regulated by acetylcholine.

Acetylcholine↗
PubMed1990

Cysteamine induces cholecystokinin release from the duodenum. Evidence for somatostatin as an inhibitory paracrine regulator of cholecystokinin secretion in the rat.

To determine whether cholecystokinin secretion is regulated by endogenous somatostatin, somatostatin deficiency was induced in vivo with cysteamine (250 mg/kg body wt, IV) or anti-somatostatin antiserum in anaesthetized rats and in vitro with cysteamine (30 micrograms/mL) in a rat duodenum-incubation system. Cholecystokinin secretion was assessed in vivo by measuring amylase in duodenal perfusates collected at 10-minute intervals for 1 hour and in vitro by a carboxy-terminal radioimmunoassay. Cysteamine induced a marked decrease in duodenal immunoreactive somatostatin both in vivo (50%) and in vitro (60%). The rate of amylase secretion increased from 9.7 +/- 2.1 U (mean +/- SE) to 28.0 +/- 4.8 U at 20 minutes (P less than 0.001). The cholecystokinin-receptor antagonist CR-1392 abolished amylase response for 30 minutes, whereas the more potent antagonists Asperlicin (18.0 mg/kg body wt, IV) and L-364,718 (0.25 mg/kg body wt, IV) caused prolonged blockade. The rate of amylase secretion in gastrectomized animals increased from 7.2 +/- 2.0 U to 15.0 +/- 2.2 U 20 minutes after cysteamine administration (P less than 0.01), indicating that the effect was not due to the presence of gastrin. In vitro, cysteamine caused a nearly fourfold increase in cholecystokinin secretion compared with controls (63.1 +/- 4.9 vs. 15.2 +/- 3.7, respectively; P less than 0.001). In vivo immunoneutralization of circulating somatostatin with a high-affinity and high-capacity antiserum produced no significant change in the rate of amylase secretion. These results suggest that cholecystokinin secretion is tonically inhibited by somatostatin and that this effect is mediated by locally secreted (paracrine) but not by circulating somatostatin.

Amylases↗
PubMed1990

Somatostatin mediates bombesin inhibition of chloride secretion by rectal gland.

The function of bombesin-like peptide, a neurotransmitter present in nerve fibers of elasmobranch rectal glands, is unknown. Since the principal activity of the rectal gland is to secrete chloride, the effects of bombesin on chloride secretion and the role of somatostatin in this response was studied. Bombesin failed to stimulate secretion in rectal glands perfused in the basal state. When added to glands stimulated by a constant infusion of vasoactive intestinal peptide (VIP), bombesin (8 x 10(-7) M) reversibly inhibited chloride secretion by 56 +/- 9.7% and at the same time evoked a 10-fold increase in the liberation of somatostatin into the venous effluent. Inactivation of somatostatin by the addition of cysteamine partially suppressed the inhibitory effect of bombesin on glandular secretion. The effect of bombesin to reduce chloride secretion was completely prevented by the calcium channel blocker nifedipine, which inhibits neurotransmitter release. These results suggest that bombesin inhibits the effect of VIP to stimulate chloride secretion by releasing somatostatin from neurosecretory nerve terminals within the rectal gland.

Animals↗
PubMed1990

Prolactin circadian rhythm persists throughout lactation in women.

To determine whether the prolactin (PRL) circadian rhythm, with its characteristic nocturnal rise, persists during the hyperprolactinemia of lactation, PRL levels were analyzed in blood samples collected hourly for 24 h from 20 mothers, 4-46 months postpartum. The circadian rhythm of PRL persisted throughout lactation as manifested by: (1) significantly higher mean nighttime than daytime PRL levels in the whole sample, despite higher daytime nursing durations; (2) the distribution of zenith levels which most frequently occur between 23.00 and 07.00 h, when nursing duration is lowest, and which are almost absent between 07.00 and 23.00 h, when nursing duration is highest, and of nadir levels, which have an opposite pattern; (3) spontaneous PRL surges that are more frequent, longer, and of higher magnitude at night than during the day, and (4) the larger magnitude of suckling-induced PRL release from late afternoon through the night compared to the morning in some women. Our data suggest that the mechanisms responsible for the circadian rhythm in PRL secretion are relatively independent of the mechanisms of suckling-induced release. We propose that the nocturnal rise in PRL during lactation functions to ensure a robust milk supply during an extensive nonsuckling interval.

Circadian Rhythm↗
PubMed1990

Estrogen regulates the gene expression of vasoactive intestinal peptide in the anterior pituitary.

Vasoactive intestinal peptide (VIP), a prolactin (PRL)-releasing factor, has been shown to be synthesized within the anterior pituitary. To test the hypothesis that estrogens increase PRL secretion, at least in part, by stimulating VIP secretion, the concentrations of VIP, peptide histidine isoleucine (PHI) and prepro VIP mRNA were measured in the anterior pituitaries of oophorectomized rats treated with 17 beta-estradiol benzoate 25 micrograms/kg/day s.c. for 5 days. For comparison, changes in the hypothalamus were also measured. Estrogen treatment resulted in a marked increase in pituitary VIP content without detectable changes in PHI content, suggesting that estrogen may regulate differentially the enzymes involved in the posttranslational processing of the VIP prohormone. A VIP mRNA-transcript of about 1.7 kilobases was detected in all tissues studied, being most abundant in the cortex, less abundant in the hypothalamus and barely detectable in the untreated pituitary. Estrogen treatment resulted in an increase in VIP gene expression in the pituitary but not in the hypothalamus or cerebral cortex. This marked increase in prepro VIP mRNA rendered possible the demonstration in the estrogen-treated pituitary of a second VIP transcript of about 1.0 kilobase which was present in only very low quantities in the cortex and hypothalamus. We conclude that estrogen regulates the gene expression of VIP in the anterior pituitary. Changes in VIP secretion may contribute to the stimulatory effect of estrogen on PRL secretion.

Animals↗
PubMed1990

Intrinsic pituitary interleukin-1 beta is induced by bacterial lipopolysaccharide.

Using a specific antiserum recognizing recombinant rat interleukin-1 beta (IL-1 beta), immunoreactive material was localized to cytoplasmic granules in anterior pituitary endocrine cells and colocalized with TSH in thyrotropes. Authenticity was established by Northern blot hybridization using a specific rat IL-1 beta cRNA probe, revealing a 1.8-kilobase mRNA identical to that in the spleen. The marked increase in anterior pituitary IL-1 beta message after the administration of bacterial lipopolysaccharide, raises the possibility that IL-1 beta may be involved in paracrine or autocrine regulation of pituitary function during infectious challenge.

Animals↗
PubMed1979

Selective transsphenoidal adenomectomy in women with galactorrhea-amenorrhea.

Thirty women with prolactin (PRL)-secreting adenomas underwent selective adenomectomy via a transsphenoidal route. All had abnormal sella polytomes or visual fields, amenorrhea with low basal serum gonadotropin levels despite decreased serum estradiol concentrations, and elevated basal serum PRL levels with blunted PRL response to neuroendocrine stimulation tests )thyrotropin-releasing hormone, levodopa, chlorpromazine, and hypoglycemia). Of 17 patients with microadenomas, 14 (82.4%) were cured and three (17.6%) improved. None were unchanged or worse. Three (60%) of five patients with larger, but still intrasellar tumors, had normalization of PRL levels, return of menses, and resolution of galactorrhea. The patients with tumors extending out of the sella did not fare as well. Overall, 21 (70%) were cured, six (20%) improved, two (6.7%) were unchanged, and the condition of one (3.3%) became worse. All preoperative neurologic deficits resolved. Postoperative complications were minimal with no neurologic morbidity. When tumors are small, surgical results are excellent with minimal risk.

Adenoma↗